1. Technical Field
The present invention relates to a method of manufacturing a substrate joint body, a substrate joint body and an electrooptical device.
2. Related Art
It is sometimes preferred that a plastic substrate is used as a base substrate for a general semiconductor applied device such as a liquid-crystal display device and an organic electroluminescence (hereinafter, “EL”) device for reasons such as that it can be manufactured at a low cost and it can prevent the device form being broken when it is deformed or dropped.
However, a thin film transistor (hereinafter “TFT”) used in a panel-type display device is manufactured through a high-temperature manufacturing process. When the TFT is formed on the plastic substrate through the high-temperature manufacturing process or when a circuit element such as an organic EL is formed through the high-temperature manufacturing process, the substrate can be deformed by heat, the circuit element could be destroyed and an element life could be shortened. In this way, a desired semiconductor applied device could not be manufactured.
A transfer technique to form the semiconductor applied device has been recently proposed (for example, see Japanese Unexamined Patent Publication No. 2003-031778). In the transfer technique as shown in FIG. 20, after a TFT 101 is formed on a heat-resisting base substrate 102 by a commonly used semiconductor manufacturing technique including the high-temperature process, an element forming film (layer) in which the TFT 101 is formed is separated from the base substrate 102. Then, this separated film is applied to a wiring substrate 103 comprising the plastic substrate and the like. Such a transfer technique makes it possible to form circuit elements without exposing the plastic substrate and the circuit elements such as the organic EL element to the high-temperature process. This means that it is possible to prevent the substrate from being deformed by heat or to prevent the circuit elements from being destroyed and a fine semiconductor applied device can be provided.
As one way to couple a wiring pattern 104 in the substrate to the TFT 101 by using the above-mentioned transfer technique, it is proposed that the wiring pattern 104 is coupled to the TFT 101 through a bump 105 formed above the wiring pattern 104 and through conductive particles 106.
Moreover, as a method of forming the above-mentioned bump 105, plating, studs and the like can be used. Plating is often adopted since it is possible to form the bump 105 in a micron-order area and shorten a takt time. In addition, it excels in height uniformity. Furthermore, there are electrolytic plating and electroless plating processes. Electroless plating is preferable since it eliminates a step of forming a base electrode and a photolithography process, and also it is possible to shorten the takt time and lower the production cost.
In the above-described transfer technique, when accuracy of the height of the bump 105 suffers, printing precision of the conductive particles 106 (discharge rate, shape and a accuracy of position) lowers and/or a trapping or capturing rate of the conductive particles 106 is low, or when the substrate is warped by the heat and pressure at the time of the transfer, poor electrical contacts may occur because the electric continuity of the TFT 101 cannot be secured. When the heat and pressure at the time of the transfer are raised to reduce the potential for poor electrical contacts to occur, the TFT 101 could be damaged and destroyed.
The present invention has been developed in consideration of the above-mentioned problems, and is intended to provide a method of manufacturing a substrate joint body with which conduction between an element and a wiring substrate can be securely obtained without damaging or destroying the element. The present invention is also intended to provide a substrate joint body and an electrooptical device.